A Study in Violet
African Violets are easily propagated through cuttings. Simply snip off a leaf, put the end of that leaf in water or soil and over time, voila, you have another plant. Ordinarily, the new plant is genetically identical to the original; it’s a clone. So why is it that when I take cuttings from my African Violet with purple flowers, the cuttings grow into plants with only white flowers?
What made my violet not violet?
One possibility could be the environment. Factors such as temperature and soil pH have been known to affect flower color. However, both the purple flower plant and the white flower plants are in the same kind of soil, so that rules out that possibility.
Another explanation could be mutation. Sometimes changes to the plant’s genes can occur during stress, such as the mechanical damage caused when cutting off a leaf. These mutations can effect flower color, shape or texture. Hobbyists and expert African Violet growers call these mutants “sports.” There are thousands of documented sports, each with a different appearance and interesting name, such as “Blue Thunder,” “Candy Swirls,” or “Victorian Flirt.” Some growers go to great lengths to discover new sports by growing cuttings under stressful circumstances, such as very high temperatures and extreme pHs, to try and induce genetic changes. However, every cutting from my purple flower plant produces a white flower plant. If mutation was the cause, it would have to be the same random mutation every time. That seems highly unlikely.
That leads us to the third and most probable possibility, hybrid reversion. Hybrids are the result of breeding together two closely related species. In the plant world, this occurs naturally and has been a driving force for speciation. Growers use hybridization to move desirable traits, such as disease resistance, drought tolerance, flower color, fruit size or yield, etc., from one plant to another. The problem is that mixing two different genomes can result in an unstable situation.
Imagine merging two shops that sell wildly different products, like a skate board shop and a store that sells geriatric care products. Which employees do you retain? Can you create a new logo that says “I’m young and rebellious but would also like to avoid a hip fracture?” Will the catheter display in the window drive away teens? Sometimes the merger can stabilize and succeed. Sometimes one store is going to become dominant, and those cool kids will just have to go somewhere else to get their skating apparel.
Hybrids are kind of like that. Two sets of genomes need to learn to work together, and this can result in huge changes. Genomes can expand or shrink. Genes can be silenced. Chromosomes battle for dominance. Sometimes, the genomes stabilize and all future generations are a healthy mix of both species. Sometimes, one species’s genes win out and become dominant over the generations.
Why are my African violet cuttings producing white flowers? The most likely explanation is that the plant with purple flowers is a hybrid, and its genome is unstable. When it produces a plant from a cutting, the original parental genes become dominant in the newly divided cells, and the resulting plant produce flowers that are more like the original. It’s reverting.
Elementary . . . I think.
Brian Rutter, PhD, is the cofounder of Thing in a Pot Productions and a postdoctoral researcher in plant biology at Indiana University. Subscribe to our newsletter to receive our “Things About Things – Odd Facts About Plants” and video production tips in your inbox every month!
Works Cited:
“African Violet Sports.” africanvioletsocietyofamerica.org, 3 July 2022, https://africanvioletsocietyofamerica.org/participate/plant-registration/african-violet-sports/
“African Violet Sports: What Are They and How Do They Occur?” baby violets.com, 3 July 2022, https://www.babyviolets.com/african-violet-sports-what-are-they-and-how-do-they-occur/
Glombik, M., Bačovský, V., Hobza, R., & Kopecký, D. (2020). Competition of parental genomes in plant hybrids. Frontiers in plant science, 11, 200.
Mallet, J. (2007). Hybrid speciation. Nature, 446(7133), 279-283.